Encoding and decoding device and method using intra prediction

ABSTRACT

An apparatus for decoding a video using an intra prediction includes: an encoded data extractor to extract filtering information, information on an intra prediction mode; an intra predictor to calculate a reference pixel characteristic by using one or more of reference pixels within neighboring blocks of the target block, determine a filtering type to be applied to the reference pixels within the neighboring blocks, based at least on the extracted filtering information and the calculated reference pixel characteristic, and generate a predicted block, by adaptively filtering the reference pixels within the neighboring blocks depending on the determined filtering type and then predicting the target block from the adaptively-filtered reference pixels according to the information on the intra prediction mode; a residual data decoder to reconstruct a residual block; and an adder to add the predicted block to the residual block to reconstruct the target block.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/819,153 filed Apr. 23, 2013, which is a the National Phaseapplication of International Application No. PCT/KR2011/006346, filedAug. 26, 2011, which is based upon and claims the benefit of prioritiesfrom Korean Patent Application No. 10-2010-0083026, filed on Aug. 26,2010. The disclosures of the above-listed applications are herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure in one or more embodiments relates to encodingand decoding apparatus and method using intra prediction.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and do not constitute prior art.

The state-of-the-art compression standard H.264/AVC enhances codingperformance based on predictions using high correlations betweenneighboring pixels in intra coding.

The intra prediction by H.264/AVC provides a total of nine predictionmodes for a block of 4×sized unit as illustrated in FIG. 1A, and a totalof four prediction modes for a block of 16×16 sized unit as illustratedin FIG. 1B.

Meanwhile, H.264/AVC provides a total of nine intra prediction modes fora block of 8×8 sized unit as with the block of 4×4 sized unit, and firstapplies a filter for removing high frequency components to referencepixels of the neighboring blocks to be used for the prediction to smooththe reference pixels prior to performing the prediction [Document 1]. Inthe filtering process, the neighboring pixels may be changed to havevalues more suitable for the intra prediction to decrease intraprediction errors for target blocks.

However, the inventor(s) has experienced that the filtering for removinghigh frequency components of the reference pixels attenuates ACcomponents actually present among original pixels, such that it isdifficult to provide details of block data to be predicted and in somecases, prediction performance or efficiency is relatively more degradedthan the case in which the filtering is not applied.

An adaptive filtering method was proposed by Fraunhofer Heinrich HertzInstitute (hereinafter, referred to as HHI) in HEVC that is a meetingfor establishing a standard of the next-generation moving picturecompression encoding/decoding device [Document 2].

The adaptive filtering method proposed by the HHI compares theprediction error occurring when the filtering for removing highfrequency components is applied to each block for intra predictionagainst the prediction error occurring without the same filteringapplied and as a comparison results, applies the smaller predictionerrors to the actual encoding, thereby reducing the prediction errors.

However, the inventor(s) has experienced that the decoding apparatusrequires an additional amount of information for each prediction blockunit to perform indexing of whether or not to apply filtering, which mayrather cause deteriorated compression efficiency for such images thatwould show little decrement of prediction errors with the adaptivefiltering.

[Document 1]

1. Telecommunication Standardization sector of ITU, ““ITU-TRecommendation H.264, Series H: Audiovisual and Multimedia Systems,Advanced video coding for generic audiovisual services””, ITU-TRecommendation H.264, pp. 132 -133, Nov 2007.

2. Martin Winken, Sebastian BoββBe, ““Description of video codingtechnology proposal by Fraunhofer HHI””, Joint Collaborative Team onVideo Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, CfPresponse proposal JCTVC-A116, Apr 2010

SUMMARY

An embodiment of the present disclosure provides an apparatus fordecoding a video using an intra prediction, the apparatus comprises anencoded data extractor, an intra predictor, a residual data decoder andan adder. The encoded data extractor is configured to extract filteringinformation, information on an intra prediction mode to be applied to atarget block and a transformed and quantized residual blockcorresponding to the target block. The intra predictor is configured tocalculate a reference pixel characteristic by using one or more ofreference pixels within neighboring blocks of the target block,determine a filtering type to be applied to the reference pixels withinthe neighboring blocks, based at least on the extracted filteringinformation and the calculated reference pixel characteristic, andgenerate a predicted block, by adaptively filtering the reference pixelswithin the neighboring blocks depending on the determined filtering typeand then predicting the target block from the adaptively-filteredreference pixels according to the information on the intra predictionmode. The residual data decoder is configured to reconstruct a residualblock by inversely quantizing and then inversely transforming thetransformed and quantized residual block. And the adder is configured toadd the predicted block to the residual block to reconstruct the targetblock.

Another embodiment of the present disclosure provides a method performedby an apparatus for decoding a video using an intra prediction, themethod comprising: extracting filtering information from encoded data;calculating a reference pixel characteristic by using one or more ofreference pixels within neighboring blocks of the target block;determining a filtering type to be applied to the reference pixelswithin the neighboring blocks, based at least on the extracted filteringinformation and the calculated reference pixel characteristic;generating a predicted block, by adaptively filtering the referencepixels within the neighboring blocks depending on the determinedfiltering type and then predicting the target block from theadaptively-filtered reference pixels; reconstructing a residual block ofthe target block from the encoded data; and reconstructing the targetblock by adding the predicted block to the residual block.

DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are diagrams of an intra prediction mode;

FIG. 2 is a block diagram of an encoding apparatus according to at leastone embodiment of the present disclosure;

FIG. 3 is a block diagram of a configuration of an intra predictor ofthe encoding apparatus according to at least one embodiment of thepresent disclosure;

FIG. 4 is a diagram of a configuration of a reference pixelcharacteristics extractor 320 according to at least one embodiment ofthe present disclosure;

FIG. 5 is a diagram for illustrating an area applied with Sobel Maskwithin neighboring blocks for detecting edges;

FIG. 6 is a block diagram of a configuration of a first intra predictorfor performing an adaptive filtering-based intra prediction according toat least one embodiment of the present disclosure;

FIG. 7 is an exemplary diagram of the first intra predictor forperforming the adaptive filtering-based intra prediction according toone or more embodiment of the present disclosure;

FIG. 8 is a flow chart of an encoding method according to at least oneembodiment of the present disclosure;

FIG. 9 is a block diagram of a configuration of a decoding apparatusaccording to at least one embodiment of the present disclosure;

FIG. 10 is a block diagram of a configuration of an intra predictor ofthe decoding apparatus according to at least one embodiment of thepresent disclosure; and

FIG. 11 is a flow chart of a decoding method according to at least oneembodiment of the present disclosure.

DETAILED DESCRIPTION

Some embodiments of the present disclosure provides encoding anddecoding apparatus and method which determine reference pixelcharacteristics of reference pixels included in neighboring blocks of atarget block to be encoded or decoded and use the determination as abasis for performing any one of the adaptive filtering-based intraprediction or the typical intra prediction to decrease the required bitamount representing whether a filtering is performed, thereby improvingcoding efficiency.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In the followingdescription, like reference numerals designate like elements althoughthey are shown in different drawings. Further, in the followingdescription of the present embodiments, a detailed description of knownfunctions and configurations incorporated herein will be omitted for thepurpose of clarity.

Additionally, in describing the components of the present disclosure,there may be terms used like first, second, A, B, (a), and (b). Theseare solely for the purpose of differentiating one component from theother but not to imply or suggest the substances, order or sequence ofthe components. When a component were described as ‘connected’,‘coupled’, or ‘linked’ to another component, they may mean thecomponents are not only directly ‘connected’, ‘coupled’, or ‘linked’ butalso are indirectly ‘connected’, ‘coupled’, or ‘linked’ via a thirdcomponent.

FIG. 2 is a block diagram for illustrating an encoding apparatusaccording to at least one embodiment of the present disclosure.

As illustrated in FIG. 2, the encoding apparatus according to one ormore embodiment of the present disclosure may include an intra predictor210, a reference picture memory 220, a residual data encoder 230, aresidual data decoder 240, an entropy encoder 250, and an encoded datagenerator 260, and the like. Each of the intra predictor 210, theresidual data encoder 230, the residual data decoder 240, the entropyencoder 250, and the encoded data generator 260 is implemented by, orincludes, one or more processors and/or application-specific integratedcircuits (ASICs) specified for respectively corresponding operations andfunctions described herein in the present disclosure. The referencepicture memory 220 includes at least one non-transitory computerreadable medium. The video encoding apparatus further comprises inputunits (not shown in FIG. 2) such as one or more buttons, a touch screen,a mic and so on, and output units (not shown in FIG. 2) such as adisplay, an indicator and so on.

Herein, the encoding apparatus may represent a personal computer (PC), anotebook computer, a personal digital assistant (PDA), a portablemultimedia player (PMP), a PlayStation Portable (PSP), a mobilecommunication terminal, and the like, and may mean various apparatusesincluding a communication device such as a communication modem thatperforms communication with various devices or wired/wirelesscommunication networks (herein, the wire or wireless networks include,for example, one or more network interfaces including, but not limitedto, cellular, Wi-Fi, LAN, WAN, CDMA, WCDMA, GSM, LTE and EPC networks,and cloud computing networks), a memory that stores various programs anddata to encode images, a microprocessor that executes programs so as toperform calculation and control, and the like.

A video to be encoded may be input in a block unit, and the block may bea macroblock. For convenience of explanation, in at least one embodimentof the present disclosure the macroblock is defined as a 16×16 form bythe same method as a H.264/AVC standard, but a general form ofmacroblock may be M×N. In particular, M and N may each be larger than 16and may be different integers from each other or the same integer.

The intra predictor 210 uses reference pixel values available in acurrent block and neighboring blocks spatially located around thecurrent block to generate an intra prediction block of the currentblock. In this case, the intra prediction block is generated bycalculating error values between the current block and the intraprediction block for each of the available intra prediction modes andapplying an intra prediction mode having a minimum error value. Further,information on the intra prediction mode is transferred to the encodeddata generator 260 by encoding the intra prediction mode having theminimum error value.

In particular, the intra predictor 210 according to at least oneembodiment of the present disclosure extracts reference pixels includedin neighboring blocks of a target block to be encoded from the referencepicture memory 220, prior to generating the intra prediction block todetermine the reference pixel characteristics. Further, it is determinedwhether to perform an adaptive filtering-based intra prediction or atypical intra prediction based on the determined reference pixelcharacteristics, and the intra prediction block for the target block tobe encoded is generated by using any one of the prediction methods basedon the determination. The adaptive filtering-based intra predictionmeans an intra prediction method for outputting cost-efficient one ofthe resultant intra prediction after performing the high-frequencyfiltering on the reference pixels included in the neighboring blocks andthe resultant intra prediction without performing the high-frequencyfiltering. Herein, upon outputting the intra prediction result, thefiltering information indicating whether the high-frequency filtering isapplied to the intra prediction is output.

The intra predictor 210 will be described below in detail with referenceto FIGS. 3 to 7.

The result (intra prediction block) output from the intra predictionblock 210 is subtracted from the block to be encoded and therebygenerated as a residual block which is output to the residual dataencoder 230.

The residual data encoder 230 performs a transform and a quantizationoperation on the residual blocks to generate an encoded residual block.In this case, various transform methods may be used for transforming asignal of a spatial domain into a signal of a frequency domain, such asHadamard transform and discrete cosine transform, and variousquantization methods may be used, such as uniform quantization includinga dead zone and quantization matrix.

According to at least one embodiment of the present disclosure, thetransform block may have a size that does not exceed a size of theprediction block. For example, when the size of the prediction block is16×16, the transform blocks of the same size 16×16 may be used as wellas smaller 16×8, 8×16, 8×8, 8×4, 4×8, 4×4 and so on. When the size ofthe prediction block is 8×8, the transform blocks, such as 8×8, 8×4,4×8, and 4×4 that do not exceed 8×8, may be used. When the size of theprediction block is 4×4, only the 4×4 transform block may be used.Further, the size of the transform block may be selected as a referenceof rate-distortion optimization. As described above, when the size ofthe transform block does not exceed the size of the transform block, theresidual data encoder 230 divides the residual blocks into the same sizeof sub-blocks as the transform block and sequentially transforms andquantizes the sub-blocks.

According to at least one embodiment of the present disclosure, the sizeof the transform block may exceed the size of the prediction block. Forexample, when the size of the prediction block is 16×16, transformblocks may be used by the sizes such as 32×16 pixels, 16×32 pixels,32×32 pixels, 64×32 pixels, 32×64 pixels, 64×64 pixels. As such, whenthe size of the transform block is larger than that of the predictionblock, the residual data encoder 230 combines a plurality of spatiallyneighboring residual blocks to generate, transform, and quantize thecombined residual block that is equal to the size of the transformblock.

The residual data decoder 240 dequantizes and inverse transforms theresidual blocks that are transformed and quantized by the residual dataencoder 220 to reconstruct the residual blocks. The dequantization andthe inverse transform reversely perform the transform and quantizationprocesses that are performed by the residual data encoder 230 and may beimplemented by various methods. For example, the residual data encoder230 and the residual data decoder 240 may use the same transform andinverse transform processes or the same quantization and dequantizationprocesses in their pre-agreement. Alternatively, the residual datadecoder 240 may use transform and quantization process information (forexample, information on a transform size, a transform shape, aquantization type, and the like) which is generated and transferred bythe transform and quantization processes of the residual data encoder230, to reversely perform the transform and quantization processes ofthe residual data encoder 230, thereby performing the dequantization andthe inverse transform.

The residual block output from the residual data decoder 240 is added tothe prediction block reconstructed by the intra predictor 210 togenerate a reconstructed block which is stored in the reference picturememory 220 and the stored reconstructed block is subsequently used as areference picture for encoding the block to be encoded.

The entropy encoder 250 entropy-encodes and outputs the residual blockoutput from the residual data encoder 230. Although not illustrated inat least one embodiment of the present disclosure, the entropy encoder250 may encode a variety of information required to decode encoded bitstreams as well as the residual blocks. Herein, a variety of informationrequired to decode the encoded bit streams may include information on amacroblock type, information on the intra prediction mode, informationon the transform and quantization types, filtering informationindicating whether the high-frequency removal filtering is performed onthe reference pictures used for the intra prediction, and the like.

The entropy encoder 250 may use a variety of entropy encoding methods,such as context adaptive variable length coding (CAVLC) and contextadaptive binary arithmetic coding (CABAC).

The encoded data generator 260 aligns the entropy encoded residualblock, the information on the macroblock type, the intra predictionmode, and the like so as to be output as the encoded data. Further, whenthe intra predictor 210 performs the adaptive filtering-based intraprediction, the encoded data generator 260 also outputs as the encodeddata the filtering information indicating whether the filtering isperformed. However, when the intra predictor 210 does not perform theadaptive filtering-based intra prediction, no filtering information isincluded in the encoded data.

Hereinafter, the more detailed configuration of the intra predictor 210according to at least one embodiment of the present disclosure will bedescribed with reference to FIGS. 3 to 7.

FIG. 3 is a block diagram for illustrating a configuration of the intrapredictor according to at least one embodiment of the presentdisclosure.

The intra predictor 210 according to at least one embodiment of thepresent disclosure may include a reference pixel setter 310, a referencepixel characteristics extractor 320, a first intra predictor 330, asecond intra predictor 340, and the like. Each of the reference pixelsetter 310, the reference pixel characteristics extractor 320, the firstintra predictor 330, and the second intra predictor 340 is implementedby, or includes, one or more processors and/or application-specificintegrated circuits (ASICs) specified for respectively correspondingoperations and functions described herein in the present disclosure.

The reference pixel setter 310 extracts pixels (reference pixels) ofneighboring blocks of the target block to be encoded from the referencepicture memory 220. The neighboring blocks of the target block to becurrently encoded should have completed their block based encoding anddecoding processes and set the pixel values of the correspondingneighboring blocks to be referenceable by the time of encoding thecurrent block. However, some encoding processes performed may make thepixel values of the neighboring blocks to be unusable, and such unusablepixels of the neighboring blocks are processed by the reference pixelsetter 310. That is, the reference pixel setter 310 checks whether thepixel values of the neighboring blocks are present and when there areneighboring pixels that cannot be referenced, the correspondingreference values are filled with products from an arbitrary operation.

The reference pixel characteristics extractor 320 receives the referencepixel values processed by the reference pixel setter 310 to determinereference pixel characteristics and uses the determination as a basisfor determining whether to transfer the reference pixel values to thefirst intra predictor 330 that performs the adaptive filtering-basedintra prediction or the second intra predictor 340 that performs thetypical intra prediction.

Herein, the reference pixel characteristics may include statisticalcharacteristics of the reference pixels, intra-image characteristicsconfigured by the reference pixels, or the like and at least oneembodiment of the present disclosure uses dispersion as the statisticalcharacteristics and the presence or absence of edges as the intra-imagecharacteristics. However, this is only one embodiment, but is to beconstrued to be included in the scope of the present disclosure when itmay be determined which of the adaptive filtering-based intra predictionand the typical intra prediction has the excellent coding efficiency andperformance.

FIG. 4 is a diagram illustrating a configuration of the reference pixelcharacteristics extractor 320 according to at least one embodiment ofthe present disclosure. Referring to FIG. 4, the reference pixelcharacteristics extractor 320 may include a statistical characteristicsextractor 410, an edge detector 420, and a filtering determiner 430.Each of the statistical characteristics extractor 410, the edge detector420, and the filtering determiner 430 is implemented by, or includes,one or more processors and/or application-specific integrated circuits(ASICs) specified for respectively corresponding operations andfunctions described herein in the present disclosure.

The statistical characteristics extractor 410 operates the dispersion ofthe reference pixels to determine whether the dispersion is at a presetthreshold value or less. Herein, the threshold value may be determinedby various methods and as one example, the following Equation 1 may beused.

$\begin{matrix}{T = \lfloor \frac{{Qstep}^{2} + 8}{16} \rfloor} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In the above Equation 1, T represents the threshold value and Qsteprepresents the width of a quantization interval. Further, T means thelargest information among integers smaller than x.

The edge detector 420 uses the reference pixels included in theneighboring blocks of the target block to be encoded to detect whetherthe edges are present in the neighboring blocks.

The edge is a feature representing a boundary between regions within animage and corresponds to a discontinuous point. Therefore, the edges canbe detected when a change in a gradient of image brightness is obtainedusing a differentiation or partial differentiation operation or a mask(operator) performing the role of a differential operation. Among edgedetection methods using the mask, the representative method uses SobelMask. In addition to this, there are methods such as Roberts Mask, aLaplacian Mask, and Canny Mask.

At least one embodiment of the present disclosure uses the method fordetecting edges using the Sobel Mask, but is not limited thereto, andtherefore, various methods for detecting edges of an image are to beconstrued to be included in the scope of the present disclosure.

The method for extracting edges using the Sobel Mask applies thefollowing mask to an image so as to detect edges.

$\begin{bmatrix}{- 1} & {- 2} & {- 1} \\0 & 0 & 0 \\{+ 1} & {+ 2} & {+ 1}\end{bmatrix}\begin{bmatrix}{+ 1} & 0 & {- 1} \\{+ 2} & 0 & {- 2} \\{+ 1} & 0 & {- 1}\end{bmatrix}$

Since the image is configured to be two-dimensional, the gradient of theimage brightness in a vertical direction (y-axis direction) and thegradient of the image brightness in a horizontal direction (x-axisdirection) need to be obtained, in which a left mask is to obtain thegradient in a vertical direction and a right mask is to obtain thegradient in a horizontal direction.

The magnitude of the gradients is calculated by applying the two masksto the neighboring blocks, and FIG. 5 illustrates a region to which theSobel Mask is applied where different sizes of the blocks used for theprediction may change the size of the neighboring region from which theedges is to be extracted.

The magnitude of the gradients may be operated by the following Equation2 that sets a central element value (element (2, 2) of a matrix) to Gyand Gx respectively as calculated by multiplying each pixel value of animage by each of the left and right masks.

G=√{square root over (G _(x) ² +G _(y) ²)}  Equation 2

When the values of the magnitude of the gradients are larger than thepreset threshold value T, it may be determined that the edges arepresent in the corresponding regions.

When the statistical characteristics extractor 410 determines that thedispersion is at the preset threshold value or less or when the edgedetector determines that the edges are present, it is determined thatthe filtering determiner 430 does not apply the adaptive filtering totransfer the reference pixels to the second intra predictor 340 thatperforms the typical intra prediction. Otherwise, however, when thedispersion is larger than the preset threshold value and the edges arenot detected, it is determined that the filtering determiner 430 appliesthe adaptive filtering to transfer the reference pixels to the firstintra predictor 330 that performs the adaptive filtering-based intraprediction.

When the dispersion of the reference pixels is small enough toapproximate 0, the high-frequency filtered reference pixels have valuesvery close to original high-frequency-unfiltered reference pixels thatare not subjected to the high-frequency filtering. In this case,therefore, the adaptive filtering-based intra prediction is notperformed, obviating the need to use index bits for indicating whetherthe filtering is performed, thereby improving the coding efficiency.

In addition, when the edges are present in the neighboring blocks of thetarget block to be encoded, the edges may be blurred when the filteringis applied to the reference pixels to give rise to a large error. Evenin this case, therefore, the determination not to use the adaptivefiltering-based intra prediction can improve the coding performance, andas the index bits are not used for indicating whether the filtering isperformed or not, the coding efficiency can be improved.

Meanwhile, at least one embodiment of the present disclosure describesthat the reference pixel characteristics are determined using both ofthe statistical characteristics of the reference pixels and the presenceor absence of the edges, but the present disclosure is not limitedthereto, and therefore the reference pixel characteristics may bedetermined using only any one of the methods.

Referring back to FIG. 3, the first intra predictor 330 performs theadaptive filtering-based intra prediction when it is determined that thereference pixel characteristics extractor 320 applies the adaptivefilter.

FIG. 6 is a block diagram for illustrating a configuration of the firstintra predictor for performing an adaptive filtering-based intraprediction according to at least one embodiment of the presentdisclosure. Referring to FIG. 6, the first intra predictor may include alow pass filter 610, intra prediction performers 620 and 630, a costcalculator 640, and the like. Each of the low pass filter 610, the intraprediction performers 620 and 630, and the cost calculator 640 isimplemented by, or includes, one or more processors and/orapplication-specific integrated circuits (ASICs) specified forrespectively corresponding operations and functions described herein inthe present disclosure.

The low pass filter 610 removes the high frequency components from thereference pixels and transfers the reference pixels to the intraprediction performer 620 and the intra prediction performer 620 performsthe intra prediction by using the reference pixels with the highfrequency components removed and transfers the results to the costcalculator 640.

The intra prediction performer 630 performs the intra prediction byusing the values of the original high-frequency-unfiltered referencepixel and transfers the results to the cost calculator.

The cost calculator 640 calculates costs required to encode data usingthe results (that is, the intra prediction results of using thehigh-frequency filtered reference pixels) performed by the intraprediction performer 620 and costs required to encode data using theresults (that is, the intra prediction results of using thehigh-frequency-unfiltered reference pixels of operation by the intraprediction performer 630 and outputs the cost-efficient results. Herein,costs may be obtained by using rate-distortion or a bit amount requiredto encode data.

Meanwhile, when outputting the intra prediction results, the costcalculator 640 also outputs the filtering information indicating whetherthe high-frequency filtering was performed.

FIG. 7 is an exemplary diagram for explaining the first intra predictorfor performing the adaptive filtering-based intra prediction accordingto at least one embodiment of the present disclosure.

The block of size n×m to undergo the intra prediction and thereconstructed reference pixel may be represented as follows.

A target block O to be encoded in n×m sized arrangement is as follows:

$O = \begin{bmatrix}o_{0,0} & \ldots & o_{0,{m - 1}} \\\vdots & \ddots & \vdots \\o_{{n - 1},0} & \ldots & o_{{n - 1},{m - 1}}\end{bmatrix}$

A prediction block P in the arrangement of n×m generated by predictingthe target block O is as follows:

$P = \begin{bmatrix}p_{0,0} & \ldots & p_{0,{m - 1}} \\\vdots & \ddots & \vdots \\p_{{n - 1},0} & \ldots & p_{{n - 1},{m - 1}}\end{bmatrix}$

The reconstructed pixel values of the previous block are used asreference pixels for the current prediction block P. FIG. 7 illustratesan example of the reconstructed reference pixels that can be referenced.

l=[l0, . . . , ln−1]

Further, the reconstructed upper pixel values are represented asfollows.

t=[t0, . . . , tm−1, . . . ]

Further, the reconstructed left upper pixel values are defined by ‘a’.With their encoding and decoding processes completed prior to thecurrent block, the respective pixels of l, t, and a are represented by‘available’.

When the adaptive filtering is performed, the low pass filter is definedas follows as it has a length of k for smoothing the reference pixelsused for the intra prediction prior to performing the intra predictionon the original block O.

f=[f0, . . . , fk−1]

The above filter coefficients generate the smoothed reference pixelvector by applying a convolution operation as the following Equation 3to reference pixel vectors l and t.

$\begin{matrix}{{{{g_{1}(x)} = {\sum\limits_{\tau = 0}^{k - 1}\; {{f(\tau)}{l( {x - \tau} )}}}},{x = 0},1,\ldots \mspace{11mu},{n - 1}}{{{g_{2}(x)} = {\sum\limits_{\tau = 0}^{k - 1}\; {{f(\tau)}{t( {x - \tau} )}}}},{x = 0},1,\ldots \mspace{11mu},{m - 1}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

In this case, in the operation of the first and final elements (t=0,t=n−1 or t=m−1) of g1 and g2, a value of f may be exceptionally changed.

The low pass filter 610 of FIG. 6 performs the high-frequency filteringon the original reference pixels depending on the Equation 2. Inaddition, the intra prediction performer 620 uses the reference pixelvectors g1 and g2 output from the low pass filter 610 to perform theintra prediction.

Meanwhile, the intra prediction performer 630 uses the originalreference pixel vectors l and t without high-frequency filtering toperform the intra prediction.

Further, the cost calculator 640 compares the costs when the encoding isperformed using the intra prediction results based on the referencepixel vectors g1 and g2 with the costs when the encoding is performedusing the intra prediction results based on the original reference pixelvectors l and t to output the cost-efficient intra prediction results.Further, the intra prediction results output by the cost calculator 640are output along with the filtering information indicating whether theresults are from using the high-frequency filtered reference pixels ornot.

Referring back to FIG. 3, when the reference pixel characteristicsextractor determines not to apply the adaptive filtering, the secondintra predictor 340 uses the high-frequency-unfiltered reference, thatis, the original reference pixel vectors l and t to perform the intraprediction and outputs the results. In this case, as the second intrapredictor does not use the adaptive filtering method, there is no needto output the filtering information indicating whether thehigh-frequency filtering is used for the intra prediction.

According to at least one embodiment of the present disclosure asdescribed above, when the reference pixel characteristics extractor 320determines to apply the adaptive filtering, the filtering information isrequired for indicating whether the high-frequency filtering was usedthe intra prediction, but when it is determined that the reference pixelcharacteristics extractor 320 determines not to apply the adaptivefiltering, the filtering information is not required, such that the bitamount required to indicate whether there was a filtering performed maybe saved.

FIG. 8 is a flow chart for illustrating an encoding method according toat least one embodiment of the present disclosure.

The reference pixel characteristics are determined by extracting atleast one reference pixels included in the neighboring blocks of thetarget block to be encoded in step S810. Herein, the reference pixelcharacteristics may include the statistical characteristics of thereference pixels such as dispersion or the intra-image characteristicsof the images configured by the reference pixels such as the presence orabsence of the edges, and the like.

When the reference pixel characteristics are determined, it isdetermined whether an adaptive filtering is applied to the intraprediction based on the reference pixel characteristics (S820). Forexample, it may determined that the adaptive filtering is not appliedwhen the dispersion of the reference pixels is smaller than the presetthreshold value or the edges are present in the neighboring blocks, andthe like, otherwise it may determined that the adaptive filtering isapplied.

When it is determined that the adaptive filtering is not applied, theintra prediction is performed by using the originalhigh-frequency-unfiltered reference pixels and the results are output(S830).

However, upon determining the application of the adaptive filtering, theintra prediction is performed based on the adaptive filtering.

That is, the high-frequency filtering is performed on the referencepixels and the intra prediction is performed by using the filteredreference pixels (S840 and S850). Then, the intra prediction isperformed by using the high-frequency-unfiltered reference pixels(S860). Further, calculations are made for the costs when the encodingis performed using the intra prediction results by the steps S840 andS850 and the costs when the encoding is performed using the intraprediction results through step S860 and then the cost-efficient intraprediction results are output. In this case, the intra predictionresults are output along with the filtering information for indicatingwhether the results are with or without the use of the high-frequencyfiltered reference pixels (S870).

Hereinafter, a decoding apparatus according to at least one embodimentof the present disclosure will be described with reference to FIGS. 9and 10.

FIG. 9 is a block diagram for illustrating a configuration of thedecoding apparatus according to at least one embodiment of the presentdisclosure.

The decoding apparatus according to at least one embodiment of thepresent disclosure may include an encoded data extractor 910, an entropydecoder 920, a residual data decoder 930, an intra predictor 940, andthe like. Each of the encoded data extractor 910, the entropy decoder920, the residual data decoder 930, and the intra predictor 940 isimplemented by, or includes, one or more processors and/orapplication-specific integrated circuits (ASICs) specified forrespectively corresponding operations and functions described herein inthe present disclosure. The video decoding apparatus further comprisesinput units (not shown in FIG. 9) such as one or more buttons, a touchscreen, a mic and so on, and output units (not shown in FIG. 9) such asa display, an indicator and so on.

Herein, as with the encoding apparatus described with reference to FIG.2, the decoding apparatus may represent a personal computer (PC), anotebook computer, a personal digital assistant (PDA), a portablemultimedia player (PMP), a PlayStation Portable (PSP), a mobilecommunication terminal, and the like, and may mean various apparatusesincluding a communication device such as a communication modem thatperforms communication with various devices or wired/wirelesscommunication networks (herein, the wire or wireless networks include,for example, one or more network interfaces including, but not limitedto, cellular, Wi-Fi, LAN, WAN, CDMA, WCDMA, GSM, LTE and EPC networks,and cloud computing networks), a memory that stores various programs anddata to decode images, a microprocessor that executes programs so as toperform calculation and controlling, and the like.

The encoded data extractor 910 extracts and analyzes the receivedencoded data and transfers data for the residual blocks to the entropydecoder 920 and data required for other predictions, for example, themacroblock mode, the encoded prediction information (information on theintra prediction mode, and the like) to the intra predictor 940.

The entropy decoder 920 performs the entropy decoding on the residualblocks input from the encoded data extractor 910 to generate quantizedresidual blocks. Although not illustrated in at least one embodiment ofthe present disclosure, the entropy decoder 920 may decode a variety ofinformation required to decode the encoded data as well as the residualblocks. Herein, the variety of information required to decode theencoded data may include information on a block type, information on anintra prediction mode, information on transform and quantization types,and the like. The entropy decoder 920 may be defined by various methodsaccording to the entropy encoding method used for the entropy encoder440 of the encoding apparatus to which at least one embodiment of thepresent disclosure is applied.

The residual data decoder 930 performs the same process as the residualdata decoder 240 of the encoding apparatus according to at least oneembodiment of the present disclosure to reconstruct the residual blocks.That is, the residual blocks are reconstructed by dequantizing thequantized residual blocks received from the entropy decoder andinversely transforming the dequantized residual blocks.

The intra predictor 940 performs the intra prediction based on the intraprediction mode information extracted from the encoded data extractor togenerate an intra prediction block.

In particular, the intra predictor 940 according to at least oneembodiment of the present disclosure uses the reference pixels includedin the neighboring blocks of the target block to be decoded to determinethe reference pixel characteristics and determines whether the encodingapparatus performed the intra prediction to which an adaptive filteringwas applied, based on the reference pixel characteristics. When it isdetermined that the adaptive filtering was applied, which would haveincluded the filtering information in the encoded data received from theencoding apparatus, the filtering information is extracted from theencoded data. Further, the intra prediction is performed by using thehigh-frequency filtered reference pixels based on the extractedfiltering information or the intra prediction is performed by using theoriginal high-frequency-unfiltered reference pixels and the results areoutput. However, when it is determined that the adaptive filtering wasnot applied resulting in the absence of filtering information in theencoded data, the intra prediction is performed by using the originalhigh-frequency-unfiltered reference pixels and the results are output.

The results (intra prediction block) output from the intra predictor 940are added to the residual blocks reconstructed by the residual datadecoder 930 so as to be reconstructed as the blocks of the originalimage.

FIG. 10 is a block diagram for illustrating a configuration of the intrapredictor 940 according to at least one embodiment of the presentdisclosure.

As illustrated in FIG. 10, the intra predictor 940 according to at leastone embodiment of the present disclosure may include a reference pixelsetter 1010, a reference pixel characteristics extractor 1020, a thirdintra predictor 1030, and a fourth intra predictor 1040, and the like.Each of the reference pixel setter 1010, the reference pixelcharacteristics extractor 1020, the third intra predictor 1030, and thefourth intra predictor 1040 is implemented by, or includes, one or moreprocessors and/or application-specific integrated circuits (ASICs)specified for respectively corresponding operations and functionsdescribed herein in the present disclosure

The reference pixel setter 1010 extracts from a reference picture memorythe pixels (reference pixels) of neighboring blocks of the target blockto be encoded.

The reference pixel characteristics extractor 1020 receives referencepixel values transferred from the reference pixel setter 1010 todetermine the reference pixel characteristics and determines whether toapply an adaptive filtering. Further, the reference pixel values aretransferred to any one of the third intra predictor 1030 and the fourthintra predictor 1040 based on the determined results. Herein, thereference pixel characteristics may include the statisticalcharacteristics of the reference pixel, the intra-image characteristicsconfigured by the reference pixels, or the like.

The reference pixel setter 1010 and the reference pixel characteristicsextractor 1020 each have the same functions as the reference pixelsetter 310 and the reference pixel characteristics extractor 320 of theencoding apparatus according to at least one embodiment of the presentdisclosure, and therefore the detailed description thereof will beomitted so as to avoid the repeated description.

The third intra predictor 1030 extracts the filtering information fromthe encoded data when it is determined that the reference pixelcharacteristics extractor 1020 applies the adaptive filtering. Inaddition, when the extracted filtering information indicates that thehigh-frequency filtering is performed, the high-frequency filtering isperformed on the reference pixels and the intra prediction is performedusing the high-frequency filtered reference pixels. However, when theextracted filtering information indicates that the high-frequencyfiltering is not performed, the high-frequency filtering is notperformed and the intra prediction is performed using the originalreference pixels and the results are output.

When it is determined that the reference pixel characteristics extractor1020 does not apply the adaptive filtering, the fourth intra predictor1040 performs the intra prediction by using the originalhigh-frequency-unfiltered reference pixels and outputs the results.

The reference pixel characteristics extractor 1020 of the decodingapparatus has the same configuration as the reference pixelcharacteristics extractor 320 of the encoding apparatus.

Therefore, when it is determined that the reference pixelcharacteristics extractor 1020 of the decoding apparatus applies theadaptive filtering, as it means that the reference pixel characteristicsextractor 320 of the encoding apparatus equally determined to apply theadaptive filtering, the filtering information is included in the encodeddata output by the encoding apparatus. Therefore, the third intrapredictor 1030 extracts the filtering information from the encoded dataand performs the intra prediction based on the filtering information.

On the other hand, when the reference pixel characteristics extractor1020 of the decoding apparatus determines not to apply the adaptivefiltering, which reflects nonapplication of the adaptive filtering bythe reference pixel characteristics extractor 320 of the encodingapparatus either, no filtering information then is included in theencoded data output by the encoding apparatus. In this case, therefore,the fourth intra predictor 1040 immediately uses thehigh-frequency-unfiltered original reference pixels to perform the intraprediction without considering the filtering information.

FIG. 11 is a flow chart for illustrating a decoding method according toat least one embodiment of the present disclosure.

The reference pixel characteristics are determined by extracting one ormore reference pixels included in the neighboring blocks of the targetblock to be encoded (S1110). Herein, the reference pixel characteristicsmay include the statistical characteristics of the reference pixels suchas dispersion or the intra-image characteristics configured by thereference pixels such as the presence or absence of the edges, and thelike.

When the reference pixel characteristics are determined, it isdetermined whether to apply the adaptive filtering based on thereference pixel characteristics (S1120). For example, when thedispersion of the reference pixels is at the preset threshold value orless or the edges are present in the neighboring blocks, it may bedetermined that the adaptive filtering is not applied, otherwise it maybe determined that the adaptive filtering is applied.

When it is determined that the adaptive filtering is not applied in stepS1120, the intra prediction is performed by using the originalhigh-frequency-unfiltered reference pixels and the results are output(S1130).

However, when it is determined that the adaptive filtering is applied instep S1120, the filtering information is extracted from the encoded data(S1140) and the extracted filtering information is checked (S1150). Asthe checked result, when the filtering information indicates that thehigh-frequency filtering is to be performed, the intra prediction isperformed by using the high-frequency filtered reference pixels and theresult is output (S1160). However, when the filtering informationindicates that the no high-frequency filtering is to be performed, theintra prediction is performed by using the originalhigh-frequency-unfiltered reference pixels and the result is output(S1170).

Various embodiments of the present disclosure as described abovedetermine the reference pixel characteristics included in theneighboring blocks of the target block to be encoded and determinewhether to perform the adaptive filtering-based intra prediction or thetypical intra prediction based on the determined reference pixelcharacteristics to perform the encoding, thereby reducing the generationfrequency of additional information generated by the adaptive filtering.As a result, various embodiments of the present disclosure as describedabove provide the higher compression encoding efficiency, control thestrictness and leniency of the determination criterion on whether toapply the adaptive filtering to provide the efficient rate-distortioncontrol factor of the video compression encoder, and decrease thecomplexity of the encoding and decoding processes occurring due to therepetitive filtering and the intra prediction cycles when the adaptivefiltering is omitted.

Various embodiments of the present disclosure is able to achieveadvantageous effects in effectively decreasing the generation frequencyof the index signal for the application of the additional filtergenerated by the adaptive filtering in the intra prediction to providethe higher compression coding efficiency, controlling the strictness andleniency of the determination criterion on whether to apply the adaptivefiltering to provide the efficient rate-distortion control factor of thevideo compression encoder, and eventually decreasing the complexity ofthe encoding and decoding processes occurring due to the repetitivefiltering and the intra prediction cycles when the adaptive filtering isremoved.

In the description above, although all of the components of theembodiments of the present disclosure have been described as assembledor operatively connected as a unit, the present disclosure is notintended to limit itself to such embodiments. Rather, within theobjective scope of the claimed invention, the respective components areable to be selectively and operatively combined in any numbers. Everyone of the components may also be implemented by itself in hardwarewhile the respective ones can be combined in part or as a wholeselectively and implemented in a computer program having program modulesfor executing functions of the hardware equivalents. Codes or codesegments to constitute such a program is easily deduced by a personskilled in the art. The computer program is stored in non-transitorycomputer readable recording medium, which in operation can realize someembodiments of the present disclosure. Examples of the non-transitorycomputer readable recording medium include magnetic recording media,such as a hard disk, a floppy disk, and a magnetic tape, and opticalrecording media, such as a compact disk read only memory (CD-ROM) and adigital video disk (DVD), magneto-optical media, such as a flopticaldisk, and hardware devices that are specially configured to store andexecute program instructions, such as a ROM, a random access memory(RAM), and a flash memory.

In addition, terms like ‘include’, ‘comprise’, and ‘have’ should beinterpreted in default as inclusive or open rather than exclusive orclosed unless expressly defined to the contrary. All the terms that aretechnical, scientific or otherwise agree with the meanings as understoodby a person of ordinary skill in the art unless defined to the contrary.Common terms as found in dictionaries should be interpreted in thecontext of the related technical writings not too ideally orimpractically unless the present disclosure expressly defines them so.

Various embodiments of the present disclosure have been justexemplified. Those of ordinary skill in the art appreciate variousmodifications and alterations without departing from the spirit andscope of the claimed invention. Specific terms used in this disclosureand drawings are used for illustrative purposes and not to be consideredas limitations of the present disclosure. Therefore, exemplaryembodiments of the present disclosure have not been described forlimiting purposes. Accordingly, the scope of the claimed invention isnot to be limited by the above embodiments but by the claims and theequivalents thereof.

What is claimed is:
 1. An apparatus for decoding a video using an intraprediction, the apparatus comprising: an encoded data extractorconfigured to extract filtering information, information on an intraprediction mode to be applied to a target block and a transformed andquantized residual block corresponding to the target block; an intrapredictor configured to calculate a reference pixel characteristic byusing one or more of reference pixels within neighboring blocks of thetarget block, determine a filtering type to be applied to the referencepixels within the neighboring blocks, based at least on the extractedfiltering information and the calculated reference pixel characteristic,and generate a predicted block, by adaptively filtering the referencepixels within the neighboring blocks depending on the determinedfiltering type and then predicting the target block from theadaptively-filtered reference pixels according to the information on theintra prediction mode; a residual data decoder configured to reconstructa residual block by inversely quantizing and then inversely transformingthe transformed and quantized residual block; and an adder configured toadd the predicted block to the residual block to reconstruct the targetblock.
 2. The apparatus of claim 1, wherein the intra-predictor isconfigured to predict the target block from high-frequency filteredreference pixels when the filtering type is a first type, and predictthe target block from high-frequency unfiltered reference pixels whenthe filtering type is a second type.
 3. The apparatus of claim 1,wherein the reference pixel characteristic is a variance of thereference pixels within the neighboring blocks.
 4. The apparatus ofclaim 1, wherein a size of the target block is determined among aplurality of block sizes, the plurality of block sizes including a sizelarger than 8×8.
 5. The apparatus of claim 1, wherein theintra-predictor is configured to, when at least one of the referencepixels within the neighboring blocks is unavailable, fill theunavailable reference pixel with a value calculated by a predeterminedoperation.
 6. A method performed by an apparatus for decoding a videousing an intra prediction, the method comprising: extracting filteringinformation from encoded data; calculating a reference pixelcharacteristic by using one or more of reference pixels withinneighboring blocks of the target block; determining a filtering type tobe applied to the reference pixels within the neighboring blocks, basedat least on the extracted filtering information and the calculatedreference pixel characteristic; generating a predicted block, byadaptively filtering the reference pixels within the neighboring blocksdepending on the determined filtering type and then predicting thetarget block from the adaptively-filtered reference pixels;reconstructing a residual block of the target block from the encodeddata; and reconstructing the target block by adding the predicted blockto the residual block.
 7. The method of claim 6, wherein the generatingof the predicted block comprising: predicting the target block fromhigh-frequency filtered reference pixels when the filtering type is afirst type, and predicting the target block from high-frequencyunfiltered reference pixels when the filtering type is a second type. 8.The method of claim 6, wherein the reference pixel characteristic is avariance of the reference pixels within the neighboring blocks.
 9. Themethod of claim 6, wherein a size of the target block is determinedamong a plurality of block sizes, the plurality of block sizes includinga size larger than 8×8.
 10. The method of claim 6, further comprisingbefore calculating the reference pixel characteristic: when at least oneof the reference pixels within the neighboring blocks is unavailable,filling the unavailable reference pixel with a value calculated by apredetermined operation.